Strain gage type load cells capable of measuring forces along a single axis while being relatively immune to extraneous forces and moments are known in the art. Examples of such load cells are shown in U.S. Pat. Nos. 3,994,161; 4,022,288; 4,103,545; 4,181,011; and 4,196,784. These patents show the use of a parallelogram linkage comprising two parallel relatively massive and unyielding structures interconnected by two flexure beams which are dimensioned to be relatively compliant or yieldable to forces parallel to the single axis but being otherwise substantially unyielding to extraneous forces and moments. Also shown is the placement of a sensing beam between such flexure beams, either anchored at both ends to the unyielding structures or cantilevered from only one of such structures.
It is a principal object of the present invention to provide an improved strain gage type load cell having a high degree of accuracy in response to loads parallel to a predetermined axis, while having enhanced immunity to the effects of extraneous loads and moments. It is a further object of this invention to provide such a load cell which can be accurately fabricated with a minimum of machining operations, and which has improved protection of the resilient members and strain gages from accidental overloading in any direction.